Let’s talk about what happened when Europeans first tried to settle North America. They failed and never came back. The entire Eastern seaboard was covered Native American farms and there was hardly a fertile spot left. And the Native Americans overwhelmed the settlers and drove them out.

I am, of course, talking about the Vikings who tried to settle Newfoundland and failed.

For five hundred years, Vikings lived on Greenland. Though they had superior technology, including iron, they were never able to settle North America. The Native Americans were so numerous, and the continent so thickly settled, they could never get purchase any where.

Similarly, after Christopher Columbus’s re-discovery of North America, Europeans tried time and again to settle in America. For decades, they were similarly rebuffed. The American continents was thickly settled. There were millions of Native Americans. The Atlantic coast was full of villages.

The first Europeans describe virtually every river in the Americas as fully occupied, where one could hardly go around a bend in the river before seeing another village. Missouri River. Amazon River. They were all like that. Thickly populated. Nowhere to settle, and too many people to displace.

But Europeans visiting those same places just a few decades later reported emptiness. Empty villages. Silence. Abandoned fields.

What happened?

Plagues of biblical proportions. European diseases like smallpox swept through North American, then down through South America. Decimation is an understatement, since it means one out of every ten people died. It was more like nine out of ten. Entire civilizations wiped out.

When the Pilgrims landed, a great plague had just swept through Massachusetts, like a wildfire down from Canada, laying waste to village after village. The Pilgrims settled in a Native American village that was empty, because almost everyone had died from disease. They would have never survived otherwise.

Everywhere the Europeans later went, they found the same thing. Land that had been full of American Indians were empty. The settlers attributed this to the “Hand of God.” It seemed that God was sweeping the land clear for the European settlers.

But in fact, it was disease, which the Europeans were more resistant to, which was sweeping through the Native American population like a shockwave.

Poizzaro was able to conquer Inca, which at the time had population and wealth several-fold greater than Spain, partly because smallpox had swept through the country before his arrival, killing the king and triggering a civil war.

Do Our Bodies Keep Some Pathogens Alive on Purpose?

It is often thought that our body does everything it can to fight off pathogens. And if there are any left behind in the body, then it’s because the body is unable to get rid of them completely.

The fact is, though, that this happens a lot–that we beat up the pathogens enough to vanquish it but not enough to completely eliminate it. For example, when we get infected by the Epstein-Barr virus, chickenpox, or polio, or by many other organisms, we successfully fight the infection, but instead of completely eliminating the organism, we end up with the organism becoming dormant. They stay in our body, and periodically re-activate. Or in cases like polio, some people become shedders, chronically shedding the virus.

Is it because viruses and other pathogens evolve so quickly that we can’t eliminate so many of them? That it’s a war between hosts and pathogens that’s still going on?

Perhaps not. Here is a bit of a radical theory. What if we harness the pathogens and turn them into a biological weapon? For example, let’s say there is a disease that we are relatively immune to, such as chickenpox. But to a population never exposed to chickenpox, it may be devastating. If we were able to shed the pox virus continuously or under conditions of stress such as during wartime, then we may have a survival advantage over individuals who completely eliminated the disease, because if we were engaged in territorial conflict with pox-naive populations, we could cause a viral shockwave that would proceed our arrival, wiping out the competing population.

We, like most vertebrates, have an adaptive immune system. It is impossible for even an adaptive immune system to be equally adept at defending against all pathogens, and we each have differential ability to fight off different kinds of pathogens. This depends on something called the HLA type which are inherited.

In other words, we are better able to fight off some pathogens, and other people are better able to fight off other pathogens. Obviously, if there were more pathogens we could better defend against, than pathogens we were less able to fight off, we would have a survival advantage.

Further, if we could increase the proportion of pathogens that we were better equipped to fight, then we could tilt the survival advantage in our favor.

Viral shockwave (my own term, as opposed to the more pedantic “pathogen-mediated competition”) is a little-accepted theory but I think it has tremendous explanatory powers.

Some parallels exist in the animal kingdom. For example, bacteria that secrete antibiotics to prevent growth of competing bacteria typically have antibiotics resistance genes. They secrete this poison, but they themselves are protected from the poison.

Here are a few other examples. The Aral Sea sturgeon was wiped out by a gill fluke from the introduced Caspian Sea sturgeon. The European crayfish was wiped out by North American crayfish that brought the crayfish plague. Similar thing happened to red squirrels in England when the grey squirrels were introduced, along with a parapox virus. And invasive harlequin ladybug that’s rampaging across the globe is able to wipe out competition because they carry, and are resistant to, a blood parasite called microsporidian.

The reverse can also be true. When invaders encounters a population with an endemic disease to which the invaders are susceptible, then the invasion often fails. This kept the Europeans from colonizing Africa for centuries, because they were unable to withstand malaria. Some parts of Africa were called “White Man’s Grave.” This biological ring fence was only breached with arrival of quinine in the mid-1800s–ironically, from the cinchona tree in Peru, a country which had been colonized because Americans were susceptible to European disease. Quinine, the first effective treatment of malaria, set off the “Scramble for Africa.”

In other words, pathogens kept Africa free of European colonization; pathogens allowed Europeans to colonize the Americas; and colonization of Americas gave Europeans quinine that allowed them to colonize Africa.

Later, once malaria became endemic in Americas, African slaves were brought over partly because they could resist malaria. In many colonies, the Caucasian slave holders died more quickly than the slaves.

So the idea of viral shockwave, though it sounds atypical, has multiple examples in biology and history. It is also consistent with a common biological theme: animals co-opting other organisms, either by symbiosis or by simple expropriation. For example, many animal use the bacteria in their gut to help digest food. Poisonous frogs in the Amazon collect their poison from the poisonous plants they eat, which in turn harvest the poison from the bacteria that grow on the plants. We all began life in the womb, connected to our mothers by the placenta, which is formed because of a gene we’ve adopted from a viral invader.

And it is also consistent with the fact that in wars, more people die of infections than from wounds.

Humans wage biowarfare. Does Mother Nature?

In November of 1854, a group of thirty-nine British nurses arrived in Scutari, Turkey. Britain, along with its allies, France and the Ottoman Empire, was waging a war that came later to be known as the Crimean war against Russia. The women came to tend to the wounded soldiers.

What they found was horrifying. Medicine was in desperately short supply. Sewers were backing up. Men were dying en masse. Epidemics were sweeping through the wards.

The leader of the nurses, realized that many men were dying not from wounds but from a far more pernicious source. Infections.

Through a series of adept moves and campaigns, including convincing newspapers to cover her work as result of which she became famous as the “Lady with the Lamp,” one of the first modern uses of statistics and graphs, and a 800-page report after the war to the British government, that leader, Florence Nightingale, changed practices in the military hospitals. She catalyzed changes that forever lowered the rate of deaths from infections in war.

Far more soldiers died from disease than bullets in that war. Other wars are similar. The flu pandemic of 1914 killed far more soldiers than other men.

It’s not just the wounded who die from infections. Even before the first bullets fly, before the first spear is cast, the military camps are festering pit of infections. Men, who are exhausted from marching, underfed, crowded together, mixing their parasites and dormant infections… it’s a horror story by any measures.

The result is predictable. The great Flu Pandemic of 1914, started in a military training barrack in the U.S. before ravaging across the world, striking down not just millions of soldiers but civilians as well.

And when people are stressed and underfed, dormant infections awaken. Tuberculosis. Herpes. On and on. Immune systems are weakened and can no longer keep them in check… or so it’s thought.

But what if it’s not the weakened immune system? What if it’s on… purpose? Is there a reason why your body might let dormant infections awaken in times of stress, in times of war?

This illustrates a salient point. More men die from infections than wounds in wars. It also uncovers a second salient point, which is that it is easier to kill with germs than with sharp weapons.

In the Middle Ages, cadavers of men who died from plague or smallpox were catapulted over the walls of castle. In North America, blankets infected with victims of smallpox were given or traded to Native Americans with the intent of triggering pandemics. Biowarfare is not new. In fact, it appears that it might have existed even before we were humans.

How Many Civilizations Have Been Wiped Out By Diseases?

This begs another question. How common is viral shockwave? And how often has it impacted people?

There are many mysteries of the ancients. Many ancient civilizations that have disappeared without a trace, leaving only questions. In Cambodia. In the Mediterranean. In North America. Minos. Anastazi.

We have long wondered why. Some believe they ran out of resources because they used them all. They cut down too many trees, for example. There is evidence that the territories of Anastzi had forests that were logged to extinction. Or they over-irrigated and the fields became too salty. Or climate change, like the Norse in Greenland.

But we forget one horseman that killed more people than hunger or war. Pestilence.

Is there any way to decipher how often viral shockwaves have played a role in our history? Is there any clue? There are a few. For example, a very small portion of our genome, by which I mean the the genome of the modern human, is Neanderthal. One of most common genes we have inherited from our Neanderthal cousins are immune genes–genes that protect us against infections. This is certainly no proof, but it is consistent with the viral shockwave hypothesis that of the genes we inherited from them are immune genes.

Significance

We have a tendency, because we live in a world where infections have largely been vanquished, to underestimate the importance of pathogens in evolution and biological history. When we puzzle over lost and fallen civilizations, when we try to decipher sudden collapse of populations of animals, we tend to put disease at the bottom of the list.

I rather think that if we were living two hundred years ago, when you expected to die from disease and not from heart disease, when one third of every person born died from smallpox and more than one third from childhood diarrhea cause by infections, that it would be patently obvious that pathogens was one of the primary drivers of evolution and human history.

This also suggests that the ability to “domesticate” a disease, to be able to withstand a pathogen and to harbor it within the body so that you can turn it into a weapon against other individuals, could be a competitive advantage. This would explain why we have so many infections that become endemic, why we have so many diseases with carriers (individuals who shed the organism but are outwardly unaffected, as with polio and thyphoid). This might explain, partly, why we have pathogens and diseases caused by pathogens.

About Me

Richard Chin is the Founder and CEO of KindredBio (NASDAQ:KIN), a biotech company developing drugs for companion animals. He is also an Associate Professor at UCSF, where he teaches drug development. His expertise is in clinical development and he has authored several books on clinical trials. More

The posts and opinions on this site are my own and do not necessarily represent those of KindredBio.

Nothing on this blog is medical advice. Do what your doctor tells you to do. Do not do anything she tells you not to do.